This invention relates to bucket-brigade circuits of the type described in "IEEE Journal of Solid-State Circuits," June 1969, pp. 131 to 136. Such bucket-brigade circuits comprise a plurality of stages which are all of the same kind, and of which each consists of a transistor and a capacitor arranged between the gate and the drain terminal thereof, and which are in such a way connected in series that the drain terminal of one is connected to the source terminal of the following transistor. The gate terminals of the even-numbered transistors are controlled by a first square-wave clock signal, and the gate terminals of the odd-numbered transistors are controlled by a second square-wave clock signal of the same frequency whose effective pulses fall within the intervals of the effective pulses of the first clock signal. Such bucket-brigade circuits are also referred to as shift registers or delay lines for analog signals.
A problem arises in connection with such bucket-brigade circuits in that the d.c. voltage level drifts along the bucket-brigade circuit towards higher or lower values. This d.c. voltage is composed of the d.c. voltage applied to the input of the bucket-brigade circuit and which is superimposed by the signal to be delayed, and of the d.c. component of the signal to be delayed. This drift of the d.c. voltage level in the case of bucket-brigade circuits composed of insulated-gate field-effect transistors (IGFETs), for example, is due to the fact that at low clock frequencies, a drifting of the d.c. potential in the direction towards the substrate potential is effected by the reverse current of the diffused zones while on the other hand, at high clock frequencies, the d.c. voltage level drifts in the opposite direction owing to the surface states. In bucket-brigade circuits composed of bipolar transistors, the base current of the transistors is responsible for having an effect upon the d.c. voltage level corresponding to the last-mentioned effect. In accordance with the aforementioned technical publication, level-regenerating circuits have been used to overcome the drift problem, however these circuits result in amplification of the signal to be delayed. An application of this conventional principle to bucket-brigade circuits composed of IGFETS, moreover, only permits compensation of the effect caused by the surface states while the drifting of the d.c. voltage level towards the substrate potential cannot be avoided with the aid of the conventional circuit.